Portable pneumatic drill with automatic adjustment of the tool thrust and torque



Feb. 26, 1952 P. R. F. DOSMOND 2,586,924

PORTABLE PNEUMATIC DRILL WITH AUTOMATIC ADJUSTMENT I OF THE TooL THRUST AND TORQUE 3 Sheets-Sheet 1 Filed March 5, 1947 In van #0 r P/erre Babe/7 Erna/740051770124 4/7arn 6y Feb. 26, 1952 R F DQSMOND 2,586,924

P. PORTABLE PNEUMATIC DRILL WITH AUTOMATIC ADJUSTMENT Filed March 5, 1947 OF THE TOOL THRUST AND TORQUE 3 Sheets-Sheet 2 I N VEN TO Q MELT,

Feb. 26, 1952 p DQSMOND 2586;924

PORTABLE PNEUMATIO DRILL WITH AUTOMATIC ADJUSTMENT OF THE TOOL THRUST AND'TORQUE Filed March 5, 1947 3' Sheets-Sheet 5 KNVE N'FON 47 g ALLM Patented Feb. 26, 1952 PORTABLE PNEUMA MATIC ADJUSTMENT TIC DRILL WITH AUTO- OF THE TOOL THRUST AND TORQUE Pierre Robert France, assignor corporate of France Application March In France N 4 Claims.

Pneumatic rock drilling machines of the kind used in mines and quarries and provided with a compressed air motor arranged to actuate a rotating tool by thrusting it against the rock through the pressure exerted by the compressed air are widely known.

A number of these drilling machines have proved to be heavy and cumbersome. Besides, in hitherto known types the normal operating conditions are such that they adapt themselves badly .to the variations of resistance of the different rock layers encountered by the drill tool or hit.

A first object of this invention is to provide a portable drilling machine having one end adapted to be mounted on a fixed point whereby the operators task is restricted to the pointing of the hand drill in the desired drilling direction.

Another object of the invention is to provide a drilling machine having means for automatically adjusting the tool thrust and torque according to the resistance offered by the rock layer or stratum which is being drilled.

A further object of the invention is to provide a compressed-air drilling machine comprising means for automatically adjusting the air pressure supplied to the motor and the air pressure which provides the necessary axial thrust on the tool by raising the former and reducing the latter when the rotational speed of the tool is retarded by an increase of the rock resistance durin the drilling operation.

The accompanying drawings illustrate diagrammatically by way of example one embodiment of the invention. In the drawings:

Fig. 1 is a plane view showing a practical arrangement of a pair of drilling machines according to the invention in a drift illustrated in fragmentary section.

Fig. 2 is a sectional view of the new drilling machine combined in accordance with the teachings of this invention.

Fig. 3 is a fragmentary view of the drilling machine shown in Fig. 2 illustrating another stage of operation thereof.

Referring to Fig. 1, the tubular horizontal bar (shown in plan view) is anchored on the substantially vertical walls 2 and 4 of the heading by any known means, for instance at one side with the aid of a buffer 5 slidably mounted in the tube to allow of adjusting the length of the bar according to the width of the heading and at the other side bya screw buffer 6 bearing against the wall 4. By tightly driving screw 6 the bar is made rigid with either wall.

Fernand Dosmond, Villerupt, of one-half to Forges & Ateliers de Meudon,

Meudon, France, a body 1947, Serial No. 732,435. ovember 5, 1945 The bar I and screw 6 will be so dimensioned that they shall resist the components according to the planes of the side Walls of the gallery during the excavation of the drift set up by the pair of drilling machines and the pushers thereof without excessive deformation. However, they should remain sufficiently light to enable e. g. two miners to manipulate them easily.

Each rotary borer of the pair I, I carries a pusher cylinder 8, 8 arranged coaxially with the machine and rigidly secured thereon. Slidably mounted in said cylinder is a piston 9 (and 9') whose end It] (and Hi) can be engaged into a sleeve II (and II) which serves as a support and a stop for the same. Said sleeve is connected by a joint with a collar 14 secured on the bar i Said joint should allow the sleeve and consequently the piston, cylinder and drill as a whole, being moved angularly in all directions while remaining attached to the bar. For instance, in Fig. 1, the two pins I2 and I3 (l2' and [3) are at right angles to each other and provide a joint of the Cardan type. Pin i3 is carried by the collar I4 that embraces the bar I and is clamped thereon by a screw 15 that can be manipulated easily with the aid of a hand lever l6.

As shown in Fig. 1 the rotary borer '1 drives the tool I! (frequently called the drill rod) into rotation.' It is illustrated at the beginning of the operation of boring a hole in the face 3 of the heading. Consequently, the piston 9 is still almost completely enclosed in its cylinder 3.

Figure 2 is partly an outside view of the drilling machine proper fitted with its tool or drill rod l1 and partly a sectional view taken on the axis of its pusher cylinder 8, which is secured to the cover of the drilling machine by any suitable means. Compressed air can enter the'said cylinder through the hole [8 and push the piston 9 which is sealed by a hat leather. The other end of piston 9 carries the tail piece described in Fig. 1.

The drilling machine 1 is fed with compressed air through ducts 29 and 30. Similar to normal hand-pushed drillin machines,.a casing 20 encloses the governor of the compressed air motor. The motor and the governor may be of any desired type- The motor is omitted in Fig. 2, yet a centrifugal governor is illustrated that partakes of the rotation of the motor. It is It already adapted to influence a valve 25 slidably received.

in a sleeve 21 and urged by a return springZG,

ably chosen for that Fig. 2 illustrates the positions assumed by the parts when the motor begins to rotate at a relatively high speed, which may occur for various reasons and mainly on account of a lower resistance encountered by the drilling tool or bit when drilling the rock. The flyweights 2| of the governor which partake of the rotation of the latter are slung apart by the centrifugal force, thus lifting a push member 22 that acts upon the lever 23 pivoted at 24 and upon the valve 25 by which the ports 28 in the sides of the sleeve 21 are almost completely closed.

The compressed air that is taken in through duct 30 is throttled by the restricted orifices 28 and flows to the motor at decreased pressure.

Fig. 3 illustrates the relative positions assumed by the parts when the increased resistance ofiered by the rock layer reduces the motor speed. The centrifugal force of the fiyweights 2| is no longer sufficient to overcome the added pressures of the return spring 26 and of the compressed air acting on valve 25, so that the latter has been able to move up again in its sleeve 21 and to completely uncover the orifices 28, whereby the compressed air can flow into 3| without pressure loss, the compressed air motor then running under full pressure.

What has just been stated in connection with the motor and the governor does not necessarily pertain to the invention. What is only required by the latter is the prevailing, in duct 3| through which the motor is fed, of a low pressure when the motor runs at high speed and of a high pressure when the motor runs at low speed.

The thrust regulator providing one of the features of the invention consists, as shown in Figs. 2 and 3, of a piston 34 received in a cylinder 35 and urged by a spring 38. Said piston 34 can also be urged in the reversed direction by compressed air acting from the other side. 32 sets that side of cylinder 35 into communication with the duct 3| through which the compressed air motor is fed.

The piston is formed with grooves 31, 38 with tape-ring bottoms. Their purpose is to establish communication, in definite positions of the piston 34, between duct 39 and orifice !8 or between orifice l9 and duct 40 which is open to the atmosphere.

The operation is as follows: with the motor running at high speed (the position shown in Fig. 2) the pressure in 3| is low and insufficient to move piston 34 towards the left through duct 32. The piston is driven to the right by spring 36. The compressed air that flows under full pressure into 35 is enabled to how through duct 39, groove 31 and orifice |8 into the pusher cylinder 8 below piston 9. Due to the fact that in this position of piston 34 the orifice I9 is closed by the piston, it will be appreciated that the air pressure in cylinder 8 is the same as in 3G and that consequently the thrust of the pusher cylinder is at its maximum value.

Referring now to Fig. 3, with the motor running at low speed, the pressure in 3| is a maximum and equal to the pressure in 33. Said pressure, through duct 32, acts upon piston 34. It prevails upon the force of sprin 36 which has been suitpurpose, and the piston is moved to the left. In this position the orifice I8 is closed by piston 34, but the orifice |9 communicates with 4G and with the outside through groove38. The cylinder 8 is no longer fed with compressed air and, instead, it is emptied through duct' 40. The air therein consequently is at at- A duct mospheric pressure and no thrust is exerted on piston 9.

Under these conditions when a rated speed has been established for the drilling machine if the resistance of the rock layers increases during the drilling operation the motor speed will be automatically reduced whereby a reduction of the thrust exerted on the tool on the one hand and an increase of the motor power on the other hand will be obtained simultaneously and automatically until another and more appropriate rated speed consistent with the resistance of the rock layers being drilled has been brought about.

In order that balance can be obtained between the speed, the motor power and the thrust of the pusher, the shapes and positions of the grooves 31 and 38 are properly selected for the obtainment of intermediate pressures within cylinder 8.

With this end in view, instead of making the grooves cylindrical, their outline is so designed that in every position of piston 34 (which position is dependent on the value of the pressure in 3|) the compressed air shall be so throttled between ducts 39 and IS on one hand and ducts l9 and 40 on the other hand that the pressure in cylinder 8 will rise from 0 to its maximum value as the piston 34 moves progressively from its end position at the left to its end position at the right, that is, as the pressure in 3| and 32 sinks progressively from its maximum to its minimum value.

In this manner the desired result is obtained, viz.: the thrust upon the drilling machine will be decreased automatically upon the tool encountering a high resistance whereas it will be raised to a maximum when the tool encounters but a low resistance.

Of course, the constructive realization described may be altered without departing from the scope of the invention; thus, for instance, the piston in the compressed-air pusher might be secured to the boring bar whilst its cylinder would be attached to the motor casing.

What I claim as my invention and desire to secure by Letters Patent is:

l. A pneumatic rock drilling machine with automatic tool thrust and torque regulating means, comprising a rotary tool adapted to exert a thrust against the rock to be drilled, a compressed air motor for rotatably driving said tool including a compressed-air inlet port, means for varying the cross-sectional area of -said port, a body containing said motor, a cylinder forming an extension of said body at the end thereof opposite to said tool, an air inlet port and a venting port for said cylinder, means for varying the cross-sectional areas of said ports of said cylinder, a piston slidably mounted in said cylinder and arranged to bear against a fixed support, a compressed air duct leading both to said motor inlet port and said cylinder inlet port, a centrifugal regulator rotatably driven by said motor, and connecting means between said-regulator and the means which varies the inlet port of said motor and the means which varies the inlet and venting ports of said cylinder, to raise the pressure of the air supplied to said motor and reduce the pressure in said cylinder as the rotational speed of said motor decreases.

2. A pneumatic rock drilling machine with automatic tool thrust and torque regulating means, comprising a rotary tool adapted to exert a thrust against the rock to be drilled; a compressed air motor for rotatably driving said tool including an air inlet port, a valve memberfor varying the opening of said port, a body containing said motor, a cylinder forming an extension of said body at the end thereof opposite to said tool, anair inlet and a venting port in said cylinder, a slide valve member mounted for sliding movement between two outermost positions, said valve member when in an intermediate position closing partially said two ports whilst completely opening one port and closing the other port when in each of said outermost positions, a piston slidably mounted alternately in said cylinder and adapted to bear against a fixed support, a compressed air duct leading to both said motor inlet port and cylinder inlet port, a centrifugal regulator rotatably driven by said motor and connecting means between said regulator and said valve members to increase the opening of the inlet port of said motor to increase the pressure of the air supplied to said motor and to decrease the opening of the inlet port of said cylinder while increasing the opening of said venting port to reduce the pressure in said cylinder as the rotational speed of said motor decreases.

3. A pneumatic rock drilling machine with automatic tool thrust and torque regulating means, comprising a rotary tool adapted to exert a thrust against the rock to be drilled, a compressed-air motor for rotatably driving said tool, including a compressed-air inlet port, a valve arranged for motion between two extreme positions, said valve partially closin said port when in an intermediate position while uncovering or closing said port completely when in said extreme positions, a spring urging said valve toward the extreme position in which said port is fully open, a'body containing said motor, a cylinder forming an extension of said body at the end thereof opposite to said tool, an air inlet port and a venting port in said cylinder, a slide valve adapted to move between two extreme positions, said slide valve partially closing said cylinder ports when in an intermediate position whilst completely uncovering one and closing the other of said cylinder ports alternately when in said extreme positions, a piston mounted for sliding motion in said cylinder and arranged to bear against a fixed support, a compressed-air supply comprising ducts leading to both said motor inlet port and cylinder inlet port, centrifugal regulator rotatably driven by said motor, mechanical means actuated by said regulator for adjusting the position of said first mentioned valve to raise the pressure of the air supplied to said motor as the rotational speed of said motor decreases and means-actuated directly by the pressure of the air supplied to'said motor for adjusting the position of said slide valve to reduce the air pressure in said cylinder as the air pressure supplied to said motor is increased owing to the reduced rotational speed of said motor.

4. A pneumatic rock drilling machine with automatic tool thrust and torque regulating means, comprising a rotary tool adapted to exert a thrust against the rock to be drilled, a compressed-air motor for rotatably driving said tool including an air inlet port having a variable cross-sectional area, a body containing said motor, a cylinder forming an extension of said body at the end thereof opposite to said tool, an inlet port and a venting port in said cylinder, a slide valve mounted for sliding motion between two extreme positions, said valve when in an intermediate position partially closing said two ports Whilst completely uncovering one port and closing the other port alternately when in each of said extreme positions, a spring bearin against one end of said slide valve and urging same torwards that extreme position thereof in which said cylinder inlet port is fully uncovered and said cylinder venting port fully closed, the other end of said slide valve communicating through a duct with the air supplied to said compressedair motor, a piston slidably engaging said cylinder and arranged to bear on a support, a compressedair duct leading to both said motor inlet port and said cylinder inlet port, a centrifugal regulator rotatably driven by said motor, mechanical control means actuated by said regulator for adjusting the cross-sectional area of said compressed-air motor inlet port in order to increase said area and therefore the pressure of the air supplied to said motor as the rotational speed thereof decreases, with the result that when a reduction occurs in said motor rotational speed the thrust exerted upon the end of said slide valve communicating with said inlet air is increased while compressing said spring and moving said slide valve in the direction of the progressive closing of said compressed-air inlet port and uncovering of said air-venting port in said cylinder.

PIERRE ROBERT FERNAND DOSMOND.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 977,734 Hansen Dec. 6, 1910 1,785,257 Greve Dec. 16, 1930 2,331,179 Fossum Oct. 5, 1943 

